Is it safe to take herbal supplements during pregnancy?

Question: My daughter has always taken a lot of herbal supplements, which she buys at a health food store. Now she is pregnant and she’s consuming even more of this stuff. Is this a good or bad thing to do?

Answer: There is a lot of uncertainly around herbal products—especially when used during pregnancy.

Supplements don’t go through the same testing and approval process as prescription and over-the-counter medications. The exact combination of ingredients might vary from manufacturer to manufacturer—and some may contain impurities. Suspected cases of negative reactions are occasionally reported in the medical literature. In general, though, they are not systematically studied.

“We don’t know what the impact would be in pregnancy for many herbal supplements,” says Dr. Batya Grundland, the maternity care lead for the family health team at Women’s College Hospital in Toronto.

“That doesn’t mean they’re all bad. We just lack the information to guide women in very specific ways.”

As the pregnancy progresses, women require sufficient levels of other nutrients. Among other things, iron is needed to produce additional blood for mother and child. And calcium plus vitamin D are critical for bone formation.

It’s possible to get most of the essential nutrients by eating a healthy and varied diet, says Steinberg.

Of course, morning sickness, which plagues many pregnant women, can stymie their best efforts to eat well.

A standard prenatal supplement, which can be purchased at a pharmacy, should safely provide the basics. But on the downside, a supplement—especially one containing iron—may contribute to feelings of nausea and constipation.

This gastrointestinal distress might be eased in various ways. For some women, it may be appropriate to switch to a children’s vitamin, which contains a lower dose of iron. Another option is to split a prenatal vitamin in two and take the separate halves at different times of day in order to improve tolerability.

Women shouldn’t consume extra supplements unless they are told to do so by their doctors. More is not necessarily better and may actually be harmful. High levels of folic acid, for example, can hide signs of vitamin B12 deficiency.

Yet the potential problems of excessive dosing is a hard message to get across—especially to those who are regular consumers of herbal products, says Steinberg.

“I had a patient who came in with a bag literally full of herbals that she was taking. We went through them ingredient by ingredient, checking them with a database of known and potential risks,” she recalls.

“I see a lot of women who want to do the absolutely best thing for their babies,” says Steinberg. “Rather than buying a standard prenatal supplement, they will spend extra money on ‘organic’ and ‘natural’ herbals and they could be unknowingly choosing things that are unsafe in pregnancy.”

It’s also important to keep in mind that some herbal teas might cause problems, too. Health Canada recommends that pregnant women should avoid certain teas, including those containing chamomile, aloe, coltsfoot, juniper berry, pennyroyal, buckthorn bark, comfrey, Labrador tea, sassafras, dock root, lobelia and senna leaves. Other herbal teas should be consumed in moderation—no more than two or three cups a day.

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